New Comet's Potential Mars Collision in 2014 Explained
http://www.scientificamerican.com/ar...potential-mars

The new comet C/2013 A1 (Siding Spring) was discovered Jan. 3 by the
Scottish-Australian astronomer Robert H. McNaught, a prolific
observer of both comets and asteroids who has 74 comet discoveries to
his name.

According to Elenin: "On the 19th October 2014, the comet might reach
apparent magnitude of -8 to -8.5, as seen from Mars!” (This would
make the comet 15 to 25 times brighter than Venus). "Perhaps it will
be possible to acquire high-resolution images from the Mars
Reconnaissance Orbiter (MRO)," he added.

Then there is also the small possibility that the comet could collide
with Mars.

Moving at 35 miles (56 km) per second, such a collision could create
an impact crater on Mars up to ten times the diameter of the comet's
nucleus and up to 1.25 miles (2 km) deep, with an energy equivalent
up to of 2 x 10^10 megatons!